Friday, February 10, 2012

A Russian answer to Escher’s day/night print

In the last issue of ISCC News (# 454), Hugh Fairman reported on Henry Hemmendinger’s search for an M.C. Escher print that seemed to transform from a day-lit scene to a night scene when the illumination spectrum changed. Was this a deliberate trick from clever use of more than three colorants? As is clear from Hugh’s article, it was not, but before I learned that fact, I extrapolated Henry’s search far afield, to the heartland of Russia.

In the summer of 2008 I was in Tambov, teaching Russian college students how to use English to advance their science careers (see Issue # 435, p. 6). For three weeks I stayed in the same dorm room, and every morning and evening had the same view from the same chair of a picture on the wall. By day the picture was a sun-lit landscape with some water and green shrubbery in the foreground. By night (in tungsten light) the picture appeared instead to be moon-lit, partly because the sky around the sun/moon orb was darker, but mostly because the green of the shrubbery appeared relatively lighter. The tungsten light was evidently rendering the blue sky darkly, but was raising the lightness of the shrubbery as if to mimic the Purkinje shift (shift to rod dominance in low light levels---hence greater lightness of green). Of course, the Purkinje shift here was illusory and not real, because the light was still bright enough to render colors: my cones still ruled the night.

I thought this might be an example of the art object Henry sought that conveyed two scenes in two lights due to colorant manipulation. I considered trying to purchase the picture, but even if I got a fair deal on it the trip home would not be easy. As I sat in that same chair one evening, I thought I’d have a closer look at the picture before I made my purchase offer. So I rose from the chair. Instantly the green shrubbery darkened.

Oops! This wasn’t related to metamerism at all. The shrubbery was brighter when I sat in the chair because I was receiving a specular reflection from the tungsten light. In daylight, I didn’t get a specular reflection, so that is why the shrubbery looked darker by day.

I had to marvel at this picture, which had different gloss in different areas. The shrubbery had the greatest gloss. Do reproductions in Russian dorm rooms have such texture and gloss differentiation, or was I looking at an original painting? Later I learned that, in printing, ink over-loading (hence gloss) is more likely in the green (and purple) than in other colors because more than one colorant maximizes its load. But meanwhile, I had reached the end of my skills as an art connoisseur, and the end of my time as well---I had to return home the next day.

Was this day/night trick deliberately set up? Perhaps not. Was it related to metamerism? Definitely not, unless you count the much-disparaged term, “geometric metamerism.” Alas, I couldn’t discuss the matter with Henry Hemmendinger, who by that time had gone where colors are more real and permanent.

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Charter, History, & Invitation

In fall 2006, Hue Angles began as a column for the ISCC News, devoted to tidbits of interesting lore shared by ISCC members in short-essay form. In its first year, the topics spanned color in wetland preservation, spinning disks under colored lights, personal recollections of selling color-matching systems, green in the fashion industry, how to measure color using a beer cooler, and color contextual effects. Almost any color-related topic is fair game. As of fall 2007, Hue Angles is also being posted here to facilitate lively discussion. As always, you can submit ideas or contributions for the column itself to Michael H. Brill, mbrill@datacolor.com

Hue Angles Supplement (June 2010)

Several people have recently demanded to know whether I am a “color realist”— as if they were choosing up sides for Armageddon. It seems a popular topic now. One episode (with arguments not seen since George “to be is to be perceived” Berkeley in the 18th Century) drove me to verse that reveals my true colors:

World and Mind(with apologies to Robert Frost)Some say that color’s in the world,Some say in mind.From optics bench with light pipes furledI hold with those who favor world.But since you bug me for advice —I think I know enough of dreamsTo know that there the hues are nice,And Berkeley schemesA modest price.